1. Field of the Invention
The present invention relates to a surface emitting laser, and a surface emitting laser array, a light source, and an optical module using the surface emitting laser.
2. Description of the Related Art
Surface emitting lasers that emit laser light at a wavelength in 850 nm band have been mainly used as light sources for optical interconnection. An integrated circuit (IC) driver normally drives the surface emitting laser of 850 nm band at 3.3 volts, with respect to the energy bandgap of a GaAs based quantum well of an active layer of the surface emitting laser.
However, not only the surface emitting lasers for optical interconnection, but all the surface emitting lasers are desired to reduce power consumption in the market. To reduce power consumption in such surface emitting lasers, a method of using a surface emitting laser having an oscillation wavelength of equal to or more than 850 nanometers, in which the energy bandgap of the active layer is lowered, and that can further reduce the bias voltage has been studied. By using a strained InGaAs quantum well for the active layer in order to increase the oscillation wavelength, a differential gain is increased and the power consumption can be further reduced.
Conventional surface emitting lasers having a wavelength of equal to or more than 850 nanometers have a structure disclosed in, for example, “25-Gbps operation of 1.1-μm-range InGaAs VCSELs for high-speed optical interconnections” by N. Suzuki, et al., OFA4, OFC2006. The surface emitting laser includes a selectively-oxidized current confinement layer. In the surface emitting laser, distributed bragg reflector (DBR) mirrors that are multilayer film reflection mirrors formed of a periodic structure of a high refractive index layer and a low refractive index layer are used as an optical resonator, and a p-side electrode is formed above the upper DBR mirror.